What Is a Window Cornice? (And How to Make One)

A window cornice can be to a window treatment what a cherry is to a sundae. Cornices serve the practical purpose of covering rods, rings, and other unsightly hardware, but the eye is drawn to them because they enhance the look of windows that could otherwise go unnoticed. Even the most luxurious window-dressing fabrics can seem ordinary without the crowning touch of one of these replicated ancient Greek architectural features.

It's easy to be confused by terminology when exploring different window treatments, especially when it comes to the word "cornice." Strictly speaking, a window cornice is a hard topping architectural element made from wood that is stained or painted. Its basic foundation is a three-sided box with an open bottom (and no back piece) and an enclosing top piece that creates what can be used as a display shelf.

Although it can be left unadorned, a true cornice — or what is termed an "architectural cornice" — includes a profiled crown molding projecting from the top of the wall. Crown molding is the horizontal trim often seen where the wall meets the ceiling, and it's also used at the top of classical door and window trim assemblies.

In addition to the crown molding at the top, cornices often include some combination of trim and projections decreasing in size moving toward the bottom. In ancient Greece, cornices made up the top band of the classical Greek architectural entablature, projecting to protect the walls below and serving as magnificently ornamental crowning features. Modern interior decor cornices provide a stylish way to hide window shade or drapery hardware and create a sense of uniformity in a room whose windows vary in size and height.

The confusion is caused by what has become the widely accepted and customary practice within the window-covering industry of applying the word "cornice" to a window-topping feature that for centuries was referred to as a "pelmet." Pelmets are also often made from wood, but they're fabric-covered, frequently padded, and lack the projecting crown molding found in architectural cornices. They most commonly look like three-sided, fabric-covered rectangles wrapping around the window-dressing hardware.

A cornice is also not a valance, which are short panels of fabric that can hang either alone at the top of a window or over a set of curtains or drapery panels for the purpose of decoratively covering the hardware.

If you're planning to add cornices to your windows, think of continuity, keeping in mind that the style and finish you use for your cornice should work with the interior design of your home. Any existing trim in your house, such as crown molding at the top of a wall or cornices that are already in place above door frames or other windows, should be matched if possible. If there are no preexisting trims in your home that need to be matched or complemented, you're free to choose from endless combinations and designs. Just remember to take the overall style of your interior into consideration.

There are endless variations when it comes to cornice design. If you can afford to hire a skilled craftsman or if you have skills yourself, you can have the most elaborate ornamentation you can dream up. If, however, you want an architectural detail that doesn't cost much but still looks great, definitely start rounding up your own tools because it's a breeze to put together a basic DIY crown-molding cornice.

The decision to use paint or stain on your cornice can guide the type of wood you use. For a painted cornice, most softwoods will work, including aspen, poplar, basswood, and pine. For a stained or natural-wood cornice, cherry, maple, mahogany, oak, or any other attractive hardwood is best. Just keep in mind that you may need to do a special order to get something other than what is commonly stocked by the home improvement stores.

In addition to the basic cornice box frame and lid, you'll be adding a crown molding to the top with ogee trim just below, running around the edge of the lid piece. At the bottom of the box, you'll add cap trim.

Putting it all together involves taking initial measurements that allow for clearance of the curtains and hardware you're covering, cutting all pieces (the crown molding requires compound miter cuts), assembling the frame and trim pieces with glue and nails, finishing the wood for paint or stain, and mounting the cornice.

If you've never performed miter cuts, especially compound miter cuts, you may want to practice a bit before you get going. These cuts are easily done with a miter saw, but if you're using a simple miter box, be sure to make some practice runs with wood scraps.